Professor Gregory "Gregg" O'Hara is the tritagonist of the 1998 Disney film Mighty Joe Young. He is portrayed by Bill Paxton.
He is a refuge director who convinces Jill Young that her giant gorilla Joe will be much safer from poachers if they move to Los Angeles. Jill agrees and Gregg starts to fall for Jill. But evil poacher Andrei Strasser is back for revenge on Joe and Jill and Greg must do whatever they can to save him.